What is Gatifloxacin?
Gatifloxacin is a synthetic, broad-spectrum antibiotic belonging to the fourth generation of fluoroquinolones. As a class, fluoroquinolones are known for their effectiveness against a wide range of bacteria. Gatifloxacin is bactericidal, meaning it actively kills bacteria. It is available in ophthalmic solutions (eye drops) under brand names like Zymar® and Zymaxid® to treat eye infections.
The Discontinuation of Systemic Gatifloxacin
While gatifloxacin is currently used for eye infections, it was once available in oral tablet and intravenous forms under the brand name Tequin. However, these systemic forms were withdrawn from the market in the United States and Canada. The U.S. Food and Drug Administration (FDA) determined the withdrawal was for reasons of safety and effectiveness.
The primary safety concern was the risk of serious and sometimes fatal blood sugar disturbances (dysglycemia), including both severe high blood sugar (hyperglycemia) and low blood sugar (hypoglycemia). These adverse effects were significant enough to lead to its discontinuation for systemic use. The risk of these side effects is not associated with the topical ophthalmic use of gatifloxacin due to minimal systemic absorption.
Primary Use: Bacterial Conjunctivitis
The main approved use for gatifloxacin ophthalmic solution is the treatment of bacterial conjunctivitis, commonly called 'pink eye'. This condition is an infection of the conjunctiva, the membrane that covers the white part of the eyeball and the inside of the eyelids. Symptoms often include:
- Redness in the eye
- Purulent or mucopurulent discharge (pus)
- Eyelids sticking together, especially upon waking
- Eye irritation and pain
Clinical trials have shown that gatifloxacin is effective in treating bacterial conjunctivitis, demonstrating a higher rate of bacterial eradication compared to a placebo. It is effective against common causative bacteria such as Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae.
How Gatifloxacin Works
Gatifloxacin's mechanism of action involves inhibiting two essential bacterial enzymes: DNA gyrase (topoisomerase II) and topoisomerase IV. These enzymes are crucial for the processes of bacterial DNA replication, transcription, repair, and recombination. By blocking these enzymes, gatifloxacin prevents the bacteria from replicating and repairing their DNA, which ultimately leads to bacterial cell death. This dual-targeting mechanism, characteristic of fourth-generation fluoroquinolones, enhances its potency and may reduce the likelihood of bacterial resistance developing.
Administration
Gatifloxacin eye drops are typically prescribed for a specific duration and frequency of administration by a healthcare professional. Following the prescribed administration schedule and completing the full course of treatment is crucial, even if symptoms improve, to ensure the infection is completely cleared and to prevent the development of antibiotic-resistant bacteria.
Comparison with Other Antibiotic Eye Drops
Gatifloxacin is one of several fluoroquinolone eye drops available. It is often compared to moxifloxacin and ciprofloxacin.
| Feature | Gatifloxacin (0.5%) | Moxifloxacin (0.5%) | Ciprofloxacin (0.3%) |
|---|---|---|---|
| Generation | Fourth | Fourth | Second |
| Primary Spectrum | Broad-spectrum; enhanced Gram-positive activity | Broad-spectrum; enhanced Gram-positive activity | Primarily Gram-negative; less potent against Gram-positives |
| Aqueous Humor Penetration | Moderate | High (Significantly higher than gatifloxacin and ciprofloxacin) | Low |
| Common Indication | Bacterial Conjunctivitis | Bacterial Conjunctivitis | Bacterial Conjunctivitis, Corneal Ulcers |
Studies have shown that moxifloxacin achieves higher concentrations in the aqueous humor of the eye compared to both gatifloxacin and ciprofloxacin. While high penetration is important for deeper infections, it may not be as critical for surface-level infections like conjunctivitis. Ultimately, the choice of antibiotic can depend on local resistance patterns, cost, and physician preference, as many studies show equivalent results among various antibiotics for treating uncomplicated bacterial conjunctivitis.
Potential Side Effects and Warnings
Like all medications, gatifloxacin ophthalmic solution can cause side effects. Most are mild and localized to the eye.
Common side effects include:
- Conjunctival irritation
- Increased tearing
- Eye pain or redness
- Altered or unpleasant taste (dysgeusia)
- Blurred vision
Serious side effects are rare but possible:
- Hypersensitivity Reactions: Serious allergic reactions, including anaphylaxis, can occur even after a single dose. Symptoms include rash, itching, hives, difficulty breathing, or swelling of the face, lips, tongue, or throat. If any of these occur, use should be discontinued immediately, and medical help should be sought.
- Superinfection: Prolonged use may lead to the overgrowth of non-susceptible organisms, such as fungi.
It is important for patients to avoid wearing contact lenses during treatment for bacterial conjunctivitis. The dropper tip should not be allowed to touch the eye, fingers, or any other surface to prevent contamination.
Conclusion
Gatifloxacin is a potent, fourth-generation fluoroquinolone antibiotic used topically to treat bacterial conjunctivitis. It works by killing bacteria through the inhibition of essential DNA enzymes. While its systemic use was halted due to significant safety risks related to blood sugar levels, its ophthalmic formulation is considered safe and effective for its approved indication. As with any antibiotic, it is vital to use it as prescribed by a healthcare professional to ensure the best outcome and minimize the risk of developing antibiotic resistance.
For more information on the approved uses and safety of gatifloxacin, you can review its prescribing information on the Pfizer label database.
